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| Image by Barbara Bonanno from Pixabay |
Soon after I blogged about author Kim Daly's The True Crime File, with its cautions about the sometimes-doubtful science behind modern investigation techniques, the Dallas chapter of Mystery Writers of America announced a program about polygraphy. And I wondered why True Crime hadn't even mentioned the procedure sometimes referred to as the lie detector test.
The program's presenters, psychologists Patricia Springer and Jan Blankenship, explained why "lie detector" isn't necessarily an accurate description of what happens during a polygraph examination, why the procedure's results can't be used in courtrooms, and why, despite that, it remains a widely used tool.
(Surprise -- it's used more often by employers than by law enforcement agencies!)
Patricia Springer is a former parole officer and author of numerous true crime books who has interviewed dozens of killers and appeared most recently on Oxygen's "A Marriage and a Murder," the subject of her current book. Jan Blankenship is a longtime psychotherapist and instructor in non-verbal communication.
The polygraph test, Springer said, is designed to observe physiological responses such as breathing, changes in skin conductivity, blood pressure, and body movements during questioning. Its chief use in law enforcement is an aid to interrogation, since its accuracy rate of only 92 percent has led courts to disallow its results as evidence. That and its cost -- an average of $700 -- means it's only used sparingly.
Lest they seem to dampen their audience's zest for the test, Springer and Blankenship presented an eye-opening video of a polygraph test and its aftermath that helped catch a murderer.
Springer was allowed to access the video because the criminal case in question had been closed with two convictions resulting from other evidence. No criminal suspect can be forced to take a polygraph but if they choose to do so, they effectively revoke their right to counsel with respect to the results. The defendant in the case in question, accused of killing his wife with the aid of his girlfriend, had requested a polygraph. It was not his wisest decision.
Each test consists of three parts:
- a pre-interview to confirm biological information and set the subject at ease
- the recorded test
- and a post-interview.
Leads are placed across the subject's chest and abdomen to record respiration. A blood pressure cuff is placed on the arm (or sometimes on the calf of the leg). Leads on the hand are fastened to the ring and index fingers. Finally, a motion detector is embedded in the subject's chair. A penile lead is also used for suspected sex offenders. Fortunately, that was not an issue in the video presented to the MWA audience.
Video of the test also records the subject's head movements and non-verbal tics.
Afterward, subjects must be informed whether they "passed" the test or not.
Those of us in the MWA group audience were not able to see the polygraph screen itself, but the subject's non-verbal tics were astonishing, and were the subject of Blankenship's critique.
"Two-thirds of human information," she told us, "is non-verbal. Twenty-five percent is voice tone, and only 8-9 percent is the content" -- the actual words uttered by a given person.
However, she cautioned, all these forms of communication are "contextual." That is, an anxiety response, for instance, can sometimes look like deception. Scratching can be a sign of deception or simply an itch. The observer at a polygraph looks for changes other than those normally used by the subject.
The subject in the video we saw had been told not to move, but nodded vigorously and repeatedly. He had been instructed not to address the male examiner as "sir," but did so repeatedly -- a verbal tic he did not repeat in the post-interview portion of the video. Most eerily, when asked if he had killed his wife, he said "no" but nodded his head "yes" in a sort of non-verbal Freudian slip. And he was astonished and angry when informed that he had not passed the polygraph test he had insisted on.
Since the test itself could not be used as evidence at trial, the hints provided by his "tells" had to be corroborated by other evidence. Both he and his girlfriend accomplice in the murder are now serving lengthy prison sentences.
I would suggest, at the least, that anyone normally prone to body movements -- a chronic foot tapper, finger tapper, or wiggler like me -- not consent to a polygraph if at all possible. (Spring noted that she also would be reluctant to take one.) But are there people who, even if guilty of heinous crimes, can pass a polygraph exam?
"People who are true sociopaths seem to breeze through them," Blankenship noted, "(although) psychopaths have a harder time."
She also cautioned that terms such as "sociopath" don't necessarily translate to "criminal," and people with this personality are often able to hold stead jobs.
So, does her awareness of how much about ourselves we betray non-verbally interfere with life outside of her professional practice? Does a psychologist like her spend every waking hour analyzing everyone she comes in contact with?
She laughed. "If the clock's not running, I'm not working. . . I have a big mental image (of boundaries) between myself and others. I may tell a family member who's a bonehead, 'hey, you're a bonehead,' but that's not a diagnosis!"
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